1. Field of the Invention
The present invention relates to a wheel damping suspension systems; and more particularly, to a compression and torsion damping wheel suspension system for a near zero turn radius lawnmower which enables the lawnmower to mow at greater speeds without subjecting the operator to excessive jarring due to rough lawn terrain.
2. Description of the Prior Art
Many patents address issues related to lawnmowers and other landscape equipment. Specifically, the compression and torsion damping feature at the connection to freewheeling front caster wheels is not disclosed.
U.S. Pat. No. 5,355,664 to Zenner discloses a caster wheel suspension and shaft tensioning system for turf maintenance equipment. A rotary mower has a castering wheel assembly so as to reduce rotation of the castering wheel about its support shaft. A torsion resistance mechanism is interposed between the shaft and the mower frame. The torsion resistance mechanism includes a resilient material rigidly bonded to a sleeve within which the shaft is retained. The resilient material is press fit into a housing, which is rigidly bonded to the mower frame. Alternatively, a cap housing a spring is attached by threads to the castering wheel support shaft. Rotation of the cap compresses spacers mounted co-axially on the shaft while urging the shaft in an upward direction so as to prevent axial rotation of the shaft when the castering wheel loses contact with the ground. The free wheeling front rolls of the lawnmower have a vertical shaft attached to a caster wheel encased in a resilient material thereby preventing lateral movement of a front caster wheel. The castering wheel assembly has a torsional resistance mechanism, which resists rotation of the castering wheel about its generally vertical support shaft. The torsional resistance mechanism also provides some degree of shock absorption between the castering wheel and the mower deck frame, especially to lateral (i.e. substantially horizontally acting) loads placed upon the wheel. The torsional resistance mechanism restricts the maximum angular rotation of the castering wheel support shaft to approximately twenty degrees under normal or typical loads. The torsional resistance mechanism is not in line with the axis of rotation of the caster wheel and is incapable of absorbing vertical shock to the user or suppressing sudden resistance load applied to the caster wheel by a bump on the lawn-mowing field.
U.S. Pat. No. 5,951,400 to Giere discloses a flexible coupling for use between two shafts. This is a constant velocity flexible coupling for direct drive to the wheels of a low speed light duty wheeled vehicle or 4-wheel drive steer lawn tractor having discs which flexibly couple a drive shaft to a wheel flange. The flexible coupling is for use in connecting a vehicle's drive shaft to a vehicle's wheel flange. The coupling includes first and second flexible disc members with opposed portions of the first flexible disc member rigidly connected to each other and to opposed portions on the second flexible disc member. This is a constant velocity coupling. U.S. Pat. No. 6,213,883 to Giere is a continuation in part of U.S. Pat. No. 5,951,400. The '400 patent discloses a flexible coupling for use between two shafts. The flexible coupling is appointed for use in a steerable drive shaft. The constant velocity flexible coupling is inserted between a drive shaft and driven machinery. The flexible coupling is not on a shaft that is attached to a freewheeling caster wheel not connected to drive power.
U.S. Pat. No. 5,960,614 to Jones discloses a torsion hitch for a tractor with a fence mower. This versatile hitch is attached to a tractor, which positions a ground-based implement, such as a mower, in front or to either side of the tractor. The hitch cushions or dampens movement using a torsional component over rough ground by the tractor, allowing the implement to traverse a near parallel ground direction. The mower design mows either normally over open ground or in restricted locations, such as around fences supported by posts. The '614 patent discloses a torsion hitch for a tractor with a fence mower. This system provides a hitch that has a torsion restraining member. In one embodiment, this torsion restraining member has two square cross section tubes provided with an elastomeric shock absorption element, such as rubber body. The torsion restraining member is not attached to a mower body at one end and is not connected to a free-wheeling caster wheel at the other end.
U.S. Pat. No. 6,101,796 to Wattron et al. discloses a mower including a device preventing the vibrations from being transmitted between the cutting mechanism and the carrying structure. This mower includes a cutting mechanism connected to a carrying structure by connections wherein each connection includes a device preventing at least some of the vibrations from being transmitted between the cutting mechanism and the carrying structure. The cutting mechanism includes a gear box at which are arranged cutting members. Each cutting member rotates about a respective axis of rotation which is at least approximately vertical during work. The carrying structure to which the cutting mechanism is connected includes at least one connection, which has a flexible element. The attachment between a tractor and the cutting mechanism has a plurality of connections that utilize an elastomeric ring to isolate vibrations. The elastomeric vibration-isolating ring is not attached to a shaft.
U.S. Pat. No. 6,857,254 to Melone et al. discloses a mower suspension system and method. The mower front independent suspension assembly includes a first suspension arm connected to the front of the lawnmower frame and a second suspension arm connected to the side of the lawnmower frame. The first suspension arm is connected to the front of the frame at or near the longitudinal center of the frame, while the second suspension arm is connected to the side of the frame a distance from the front of the frame. Alternatively, the cutter deck of the lawnmower is connected to the front independent suspension assemblies for movement therewith. The first and second front wheels independently movable upward and downward with respect to one another and coupled to the frame for upward and downward movement with respect to the frame. A pair of suspension arms are pivotally coupled to the frame and coupled to one of the front wheels. This lawnmower has front wheels connected to a strut that is pivoted on the lawnmower's mainframe front. The strut is provided with a compression spring adapted to cushion the ride. There are no elastomeric elements within the suspension system; the system does not respond when resistance to movement of the front wheels imparts torsion to the strut.
U.S. Pat. No. 6,912,832 to Thompson et al. discloses a mower suspension. A suspension system for a tractor-drawn mower used for crops for agricultural purposes is made up of parallel links, connected at a first end to a frame and to a mowing unit at a second end. A torsion spring assembly, similar to that used for torsion axles, is used to bear a portion of the weight of the mowing unit when the mowing unit is in a lower, mowing position. All torsional stress is removed from the torsion spring when the mowing unit is in a transport position. During mowing, the weight of the mowing unit is divided up between the torsion spring and the surface of the ground. The ratio of the weight supported by the ground to that supported by the torsion spring is adjustable by an operator. U.S. Pat. No. 7,086,214, which is a continuation-in-part of U.S. Pat. No. 6,912,832, discloses a similar mower suspension. The mover pivot uses a larger square shaped hollow tube carrying a smaller square shaped hollow tube with rubber elements as shown in FIGS. 4 and 4a to form a mower pivot. Rotation of the outer tube with respect to the inner tube, by rotation of the torsion arm, results in compression of rubber elements 306. The mower pivot is not attached within an offset shaft that connects a pivot axis and a freewheeling caster front wheel of a lawnmower.
There remains a need in the art for a compression and torsion damping wheel suspension system that dampens compressive vertical forces when the professional landscape lawnmower front freewheeling caster wheels traverse a bump in the field or a rock. Also needed in the art is a wheel suspension system that dampens the torsional load when one or both of the front freewheeling caster wheels encounter resistance. Such compressive or torsional forces jar the operator of the professional landscape lawnmower, limiting severely the lawn mowing speed. In the worst case, the rear traction wheels of the professional landscape lawnmower lifts and loses contact with the ground, losing traction and even turning and pointing the professional landscape lawnmower in an unwanted direction.